Two roads, two levels of certainty
The short road is knowable from the outset: one office, one certificate, one published rate. The long road leaves that first section unchanged and adds a stage governed elsewhere, with a charge and a pace of its own. An apostille from United Kingdom to Yemen runs the long road, so half of it can be quoted exactly and half of it can only be allowed for.
Where Yemen stands
Yemen has not joined the Hague Apostille Convention. That single point decides the shape of the whole corridor: it places a consular desk after the British one, and it is the reason the total cost of the route cannot be stated as one figure. The status itself is settled and is not in dispute; what follows from it is where the open questions sit.
The part that runs to a fixed procedure
Leicester Registration Service at 115 Charles Street, Leicester LE1 1FZ prints certified copies of births, marriages and deaths registered locally. The FCDO Legalisation Office at PO Box 6255, Milton Keynes MK10 1XX certifies the signature on that copy and returns it by post; there is no counter to attend. Both bodies behave the same way on every file they touch.
One figure, honestly bounded
The British charge is £45 a document by standard post, or £40 a document next-day for a sender that is a registered business, and it attaches to each document rather than to the envelope. That is the published part. Treating it as the price of the corridor understates the corridor, because the consular stage brings a second official charge with it.
Planning around a gap
A gap in what can be quoted is not a gap in what can be done. Order the copies early, keep the certified bundle intact and whole, and build in slack for the stage whose length nobody has published. What this corridor punishes is not ignorance of the second charge but a schedule that quietly assumes the first stage was the last one.